Method of controlling rotation of a V-belt drive

ABSTRACT

A method of controlling the speed of the output of a V-belt drive having an output driven pulley driven by a V-belt from an input driver pulley wherein the rotational speed of the driver pulley is determined, the ratio of the effective belt drive diameters of the driver and driven pulleys are determined and the effective belt to drive diameter of at least one of the pulleys is adjusted to provide a preselected speed of the drive output.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to V-Belt drives and more particularly toa method of controlling the speed of a driven shaft not withstandingvariations in the speed of a driver shaft.

2. Description of Background Art

A V-Belt power transmission drive including a driver pulley, a drivenpulley and a V-belt interconnecting the pulleys is a common method oftransmitting torque from a prime mover to a load. While the angularvelocity i.e., rotational speed, of the driven pulley is normally notequal to the rotational speed of the driver pulley, as determined by theratio of the circumference of the driven pulley to the circumference ofthe driver pulley, the speed of the driven pulley is normally directlyproportional to the speed of the drive pulley.

One use of such V-belt drives is in driving the generator of a vehicle.Such generators conventionally have optimal operating speeds. Thegenerator is driven from the automobile engine, the speed of whichvaries, so that the speed of the generator correspondingly varies.

Therefore, in such operation of the vehicle, the generator may not beoperating at the optimal speed at all times and must be designed tooperate over a wide range of driven speeds.

In other applications incorporating V-belt transmissions, the primemover has a speed-versus-torque relationship different from thespeed-versus-torque relationship of the load. Where the speed of theload is caused to be directly proportional to the speed of the primemover, the prime mover must be sufficiently oversized to permit thetorque output of the prime mover at any speed to satisfy the torquerequirement of the load at the operating speed thereof. Such oversizingis undesirable for economic concerns, space requirements, ease ofmaintenance, etc.

SUMMARY OF THE INVENTION

The present invention comprehends a method of controlling the speed ofrotation of a load driven by a drive system including a driver pulley, adriven pulley and a V-belt engaged therebetween.

In the illustrated embodiment, one or both of the pulleys comprises avariable diameter pulley and include illustratively a movable pulleypiece movable with respect to a stationary pulley piece. As the movablepulley piece is adjusted in relation to the stationary pulley piece, theeffective diameter of the variable diameter pulley changes, therebychanging the ratio between the driver pulley and the driven pulley.

In the illustrated embodiment, the engine is directly connected to thedriver pulley. The driven pulley is directly connected to a load, anautomotive generator having a preselected speed-versus-torquerelationship. A V-belt interconnects the driver pulley to the drivenpulley.

The rotational speed of the driver pulley is sensed and a correspondingspeed signal is generated. The position of the movable pulley piece ofthe variable diameter pulley is adjusted in accordance with the speedsignal, thereby modulating the effective diameter of the variablediameter pulley in accordance with the load requirements. The inventioncomprehends an improved method of controlling this function.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from thefollowing description taken in connection with the drawings, wherein:

FIG. 1 is a graph illustrating the relationship between the rotationalspeed of the driver pulley and the driven pulley, for both aconventional V-belt power transmission drive and a V-belt powertransmission drive incorporating the present invention;

FIG. 2 is a graph illustrating the relationship between the rotationalspeed of a generator and the operating efficiency of the generator;

FIG. 3 is a schematic perspective view of a drive system embodying thepresent invention;

FIG. 4 is a diametric section taken substantially along the line 4--4 ofFIG. 3 illustrating the variable diameter driver pulley;

FIG. 5 is a schematic perspective view similar to that of FIG. 2, butillustrating a drive system utilizing a different method of sensing thedriver pulley speed;

FIG. 6 is a schematic diagram of the electric control utilized in theprevent invention;

FIG. 7 is a schematic diagram illustrating another electric controlsystem useful in practicing the invention;

FIG. 8 is a schematic diagram illustrating still another electriccontrol system useful in practicing the invention; and,

FIG. 9 is a schematic diagram illustrating yet another electric controlsystem useful in practicing the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A V-belt power transmission drive 15 includes a driver pulley 18connected to a prime mover engine 16, a load or driven pulley 20connected to a rotating load 21 and a V-belt 22 engaged therebetween.

FIG. 1 compares the relationship between the angular velocity, orrotational speed N_(d) of the driver pulley 18, versus the ratio of thedriven pulley speed N_(L) to the driver pulley speed N_(d) for a V-beltpower transmission drive, embodying the invention with the prior artV-belt drives.

A first curve 10 illustrates the relationship between the driver pulleyspeed (N_(d)) and the ratio of driven pulley speed to drive pulley speed(N_(L) /N_(d)) for a conventional V-belt power transmission drive. Forany driver pulley speed (N_(d)), the ratio of driven pulley speed todriver pulley speed, (N_(L) /N_(d)) remains constant. Thus, as N_(d)increases, N_(L) increases proportionately.

A second curve 12, including segments a, b, and c, illustrates therelationship between the drive pulley speed (N_(d)) and the ratio ofdriven pulley speed to driver pulley speed (N_(L) /N_(d)) for a V-beltpower transmission drive incorporating the present invention. Segment"a" of curve 12 illustrates the speed wherein the ratio of driven pulleyspeed to driver pulley speed decreases linearly as the driver pulleyspeed increases, i.e., the driven pulley speed remains constant overthis range of driver pulley speeds.

The segments "b" and "c" of the second curve 12 illustrate the ranges ofdriver pulley speeds beyond the maximum limits of adjustment of thedriver pulley diameter.

FIG. 2, illustrates the relationship between the speed of a typicalautomotive generator and the operating efficiency thereof. As indicatedat a point E in FIG. 2, there exists an optimum speed for operation ofthe generator.

FIG. 3 illustrates a power transmission drive for carrying out themethod of the present invention. As shown, V-belt drive 15 includesmotor 16 having an output shaft 23 and variable diameter driver pulley18 including a movable pulley piece 19a, and a stationary pulley piece19b connected to output shaft 23 . Driven pulley 20 is connected torotating load 21 and V-belt 22 is engaged between driver pulley 18 anddriven pulley 20.

A magnetic pickup 26, coupled to a controller 28, senses the successivejuxtaposition of projections 30a of a gear 30, driven with pulley piece19b for generating a speed signal representing the rotational speed ofdriver pulley 18.

A servo motor 34 electrically coupled to the controller 28 includes ashaft 29 supported by a bearing 30 and connected to a lever arm 36connected to movable pulley piece 19a. A position sensor 38, discussedfurther below, is mechanically connected to shaft 29. Position sensor 38is electrically coupled to controller 28, to generate a signalrepresentative of the angular position of lever arm 36 about the axis ofshaft 29, and thus representative of the position of movable pulleypiece 19a.

As motor 16 rotates driver pulley 18, V-belt 22 causes driven pulley 20to rotate. The speed of the driver pulley 18 is sensed by magneticpickup 26. Controller 28 in response to the speed signal, provides anoutput signal to servo motor 34 causing servo motor 34 to berepositioned. The repositioning of servo motor 34 rotates lever arm 36,thereby moving movable pulley piece 19a axially with respect tostationary pulley piece 19b as seen in FIG. 4.

A spring 40 is provided coaxially on a hub portion 42 of fixed pulleypiece 19band is compressed between the movable pulley piece 19a and aspring retainer 44 fixed to hub portion 42. A U-section guide ring 48 ismounted through a bearing 50 on the outer periphery of hub portion 42 ofmovable pulley piece 19a. A slide portion 36a of lever arm 36 isreceived in the guide ring 48.

Selective positioning of lever arm 36 moves movable pulley piece 19aaxially of hub portion 42, thereby correspondingly increasing ordecreasing the space between movable pulley piece 19a and stationarypulley piece 19b.

For example, when movable pulley piece 19a is moved axially away fromthe stationary pulley piece 19b, V-belt 22 moves radially inwardlyrelative to hub portion 42 to decrease the effective diameter of driverpulley 18.

Correspondingly, when movable pulley piece 19a is moved axially towardsstationary pulley piece 19b the V-belt 22 moves radially outwardlyrelative to hub portion 42 thereby increasing the effective diameter ofdrive pulley 18.

Such change in the effective diameter of drive pulley 18 correspondinglychanges the ratio of driver pulley diameter to load pulley diameter.

As seen in FIG. 5, a tachometer 26b is connected to drive pulley 18 by abelt 52 and pulleys 54 and 56. Tachometer 26b is electrically coupled tocontroller 28 and provides an alternate method of sensing the rotationalspeed of the driver pulley 18.

FIG. 6 illustrates a method of controlling the rotation of the V-beltpower transmission device embodying the present invention.

The speed signal indicating the rotational speed of driver pulley 18 isprovided by sensor 26 to controller 28 including a rotary amplifier 58,a summing junction 59 and a servoamplifier 60.

A position sensor 38a includes a potentiometer 61, a voltage source 62and a sliding contact 63 mechanically connected to lever arm 36 (FIG. 3)and electrically coupled to summing junction 59.

Summing junction 59 generates an error signal which is amplified byservoamplifier 60. Servomotor 34 responds to the amplified error signalgenerated by servoamplifier 60, thereby causing servomotor 34 to rotateand varying the effective diameter of driver pulley 18.

A change in the rotational speed of motor 16 causes a change in therotational speed of drive pulley 18, the change being sensed by sensor26. An amplified error signal, generated by controller 28, causesservomotor 34 to rotate, thereby varying the effective diameter of drivepulley 18.

Thus, the ratio of driven pulley diameter to driver pulley diameter and,correspondingly load pulley speed to driver pulley speed is modified asa function of driver pulley speed in accordance with a desiredparameter. The parameter for the particular application may comprise anoperating curve for example, established by the resistancecharacteristics of potentiometer 61.

An alternate method of sensing the angular position of lever arm 36 isillustrated in FIG. 7. A position sensor 38b includes a magnetic core 70mechanically connected to lever arm 36 and slidably movable throughprimary and secondary windings 72a and 72b of a differential transformer72. Differential transformer 72 generates an output signalcorrespondingly to the position of core 70 magnetically interconnectingprimary and secondary windings 72a and 72b. Thus the output signal ofdifferential transformer 72 is directly proportional to the position oflever arm 36 and hence, the effective diameter of driver pulley 18.

FIG. 8 illustrates still another alternate method of sensing the angularposition of lever arm 36. A position sensor 38c includes a magneticsensor 75 having magnetized metal plate 76 connected to lever arm 36. Asignal generated by magnetic sensor 75 is proportional to the positionof magnetized metal plates 76 in respect to the secondary windings ofthe magnetic sensor 75.

FIG. 9 illustrates yet another method of sensing the position of leverarm 36. A variable capacitor 77 includes a movable plate 78 mechanicallycoupled to lever arm 36. An oscillator 79, includes an amplifier 80coupling capacitator 77 to a voltage converter 81 to generate a voltagehaving a frequency determined by the capacitance of variable capacitor77. A position sensor 38d comprising oscillator 79 and voltage converter81 generates a voltage representative to the rotational position oflever arm 36.

The foregoing disclosure of specific embodiments is illustrative of thebroad inventive concepts comprehended by the invention.

I claim:
 1. The method of controlling the speed of the output of aV-Belt drive having an output driven pulley driven by a V-Belt from aninput driver pulley, comprising the steps of:determining the rotationalspeed of the driver pulley; determining the instantaneous effective beltdiameter of the driver pulley; determining the ratio of the effectivebelt drive diameters of the driver and driven pulleys; and adjusting theeffective belt drive diameter of at least one of the pulleys to providea preselected speed of the drive output.
 2. The method of controllingthe speed of the output of a V-belt drive of claim 1 wherein said stepof adjusting the effective belt diameter comprises a step of adjustingthe effective belt drive diameter of the driver pulley.
 3. The method ofcontrolling the speed of the output of a V-belt drive of claim 1 whereinsaid driver pulley comprises a split pulley having a pair of coaxialaxially variably spaced pulley pieces defining an adjustable diameterV-belt groove receiving the V-belt.
 4. The method of controlling thespeed of the output of a V-belt drive of claim 1 wherein said driverpulley comprises a split pulley having a pair of coaxial axiallyvariably spaced pulley pieces defining an adjustable diameter V-beltgroove receiving the V-belt and said step of adjusting the effectivebelt drive diameter comprises a step of adjusting the effective beltdrive diameter of the driver pulley by adjusting the axial spacing ofthe pulley pieces.
 5. The method of controlling the speed of the outputof a V-belt drive of claim 1 wherein the step of determining therotational speed of the driver pulley comprises a step of providing apulse generator driven by the driver pulley and sensing the rate ofpulse generation thereby.
 6. The method of controlling the speed of theoutput of a V-belt drive of claim 1 wherein the step of determining therotational speed of the driver pulley comprises a step of driving atachometer in correspondence with the speed of the driver pulley.
 7. Themethod of controlling the speed of the output of a V-belt drive havingan output driven pulley driven by a V-belt from an input driver pulleycomprising a split pulley having a pair of coaxial, axially variablyspaced pulley pieces defining an adjustable diameter V-belt groovereceiving the V-belt, said method comprising the steps of:determiningthe rotational speed of the driver pulley; sensing the axial spacingbetween the driver pulley pieces to determine the effective belt drivediameter of the driver pulley; determining the ratio of the effectivebelt drive diameters of the driver and driven pulleys; and adjustingsaid axial spacing between said pulley pieces to adjust the effectivebelt drive diameter of the driver pulley to provide a preselected speedof the drive output.
 8. The method of controlling the speed of theoutput of a V-belt drive of claim 7 wherein said step of adjusting saidaxially spacing includes a step of comparing the determined rotationalspeed of the driver pulley with a reference signal and providing acomparison signal for controlling said adjustment.
 9. The method ofcontrolling the speed of the output of a V-belt drive of claim 7 whereinsaid step of determining the rotational speed of the driver pulleycomprises a step of providing a speed voltage signal proportionalthereto, and said step of adjusting said axial spacing includes a stepof comparing said voltage signal with a reference voltage signalcorresponding to said axial spacing, and providing a comparison signalfor controlling said adjustment.
 10. The method of controlling the speedof the output of a V-belt drive of claim 7 wherein said step ofdetermining the rotational speed of the driver pulley comprises a stepof providing a speed voltage signal proportional thereto, and said stepof adjusting said axial spacing includes a step of comparing saidvoltage signal with an adjustable reference voltage signal correspondingto said axial spacing, and providing a comparison signal for controllingsaid adjustment.
 11. The method of controlling the speed of the outputof a V-belt drive of claim 7 wherein said step of determining therotational speed of the driver pulley comprises a step of providing aspeed voltage signal proportional thereto, and said step of adjustingsaid axial spacing includes a step of comparing said voltage signal withan adjustable reference voltage signal corresponding to said axialspacing produced by a variable potentiometer, and providing a comparisonsignal for controlling said adjustment.
 12. The method of controllingthe speed of the output of a V-belt drive of claim 7 wherein said stepof determining the rotational speed of the driver pulley comprises astep of providing a speed voltage signal proportional thereto, and saidstep of adjusting said axial spacing includes a step of comparing saidvoltage signal with an adjustable reference voltage signal correspondingto said axial spacing produced by a differential transformer, andproviding a comparison signal for controlling said adjustment.
 13. Themethod of controlling the speed of the output of a V-belt drive of claim7 wherein said step of determining the rotational speed of the driverpulley comprises a step of providing a speed voltage signal proportionalthereto, and said step of adjusting said axial spacing includes a stepof comparing said voltage signal with an adjustable reference voltagesignal corresponding to said axial spacing produced by a differentialtransformer having a core adjustably positioned in accordance with saidaxial spacing, and providing a comparison signal for controlling saidadjustment.
 14. The method of controlling the speed of the output of aV-belt drive of claim 7 wherein said step of determining the rotationalspeed of the driver pulley comprises a step of providing a speed voltagesignal proportional thereto, and said step of adjusting said axialspacing includes a step of comparing said voltage signal with anadjustable reference voltage signal corresponding to said axial spacingproduced by a differential transformer having a magnetic plateadjustably positioned in accordance with said axial spacing, andproviding a comparison signal for controlling said adjustment.
 15. Themethod of controlling the speed of the output of a V-belt drive of claim7 wherein said step of determining the rotational speed of the driverpulley comprises a step of providing a speed voltage signal proportionalthereto, and said step of adjusting said axial spacing includes a stepof comparing said voltage signal with an adjustable reference voltagesignal corresponding to said axial spacing produced by a variablecapacitor, and providing a comparison signal for controlling saidadjustment.
 16. The method of controlling the speed of the output of aV-belt drive of claim 7 wherein said step of determining the rotationalspeed of the driver pulley comprises a step of providing a speed voltagesignal proportional thereto, and said step of adjusting said axialspacing includes a step of comparing said voltage signal with anadjustable reference voltage signal corresponding to said axial spacingproduced by a variable capacitor having a movable plate adjustablypositioned in accordance with said axial spacing, and providing acomparison signal for controlling said adjustment.
 17. A method ofdetermining drive system parameters for controlling the rotation of aV-belt transmission drive system having a driver pulley, a driven pulleyopposed to the driver pulley, a belt engaged between the both pulleys asV-shaped variable speed pulleys so that a movable pulley piece of eitherone pulley is movable via bearings relative to a stationary pulley pieceby an arm for operating the movable pulley piece, the effective beltpitch diameters of the V-shaped groove formed by each variable pulley inwhich the control of the rotation of the pulleys depends on acombination of a mechanical system and an electrical control system,said method comprising the steps of:causing via a converter incooperation with the arm a variation in the position of the arm forvarying the width of the V-shaped groove of a variable pulley as avariation in voltage; introducing the variation in the voltage and thevariation in a voltage proportional to the rotating speed of the driverpulley produced from the driver pulley into a differential amplifier todetect the difference between the voltages and to output a differentialsignal in response thereto; operating a normal/reverse converter on thebasis of the differential signal automatically adjustably move themovable pulley piece so that the potential difference of the bothvoltage signals to the differential amplifier becomes zero,substantially thereby adapting the rotation of the driven pulley for apredetermined characteristic curve in response to the variation in therotation of the driver pulley; determining the effective belt pitchdiameter of each variable pulley; and calculating the ratio of theeffective belt drive diameters of the two pulleys.
 18. The method ofclaim 17 wherein a spring is provided movably on a shaft between themovable pulley piece and the stationary pulley piece.
 19. The method ofclaim 17, wherein a guide ring is mounted through a bearing on the outerperiphery of the driver pulley piece.
 20. The method of claim 19 whereinsaid guide ring is mounted on the movable pulley piece of the drivenpulley.
 21. The method of claim 19 wherein a magnetic rotary pickup isused for detecting the rotation of the drive pulley.
 22. The method ofclaim 19 wherein a variable resistor is used in cooperation with saidarm for operating the movable pulley piece.
 23. The method of claim 19wherein a plurality of driven shafts are provided, the driver pulley isprovided on one of the driven shafts, and the rotation of thetransmission is controlled between the driven pulley and the driverpulley.
 24. The method of claim 19 wherein a system for producingdirectly a speed signal is used for detecting the rotation of the driverpulley.
 25. The method of claim 19 wherein one of a differentialtransformer, a variable capacitor or a magnetic sensor is used fordetecting the rotation of the driver pulley.